1. Field of Disclosed Subject Matter
This disclosure relates to systems and methods for implementing an improved belt fuser assembly in an image forming device including employing a double belt roll fuser geometry to enable consistent self-stripping of image receiving media exiting the fuser assembly thereby improving image quality for the fused images on the image receiving media.
2. Related Art
The principles of operations in xerographic image forming devices are well known. Xerographic, and other toner-based, image forming devices include image marking units, that are generally used to transfer multiple colors of toner as the image marking medium onto an image receiving medium substrate in image forming devices including copiers, printers, facsimile machines and other like devices.
As is generally understood in xerography, for example, a photoconductive transfer element may be presented in the form of photoconductor belt. The photoconductor belt is mounted on, and driven by, a plurality of powered and follower photoconductor belt rollers. In operation, a photoconductive surface of the photoconductor belt is exposed to light images emitted from a light source as an imaging unit that optically exposes and selectively charges the photoconductive surface of the photoconductor belt to form an electrostatic latent image on the photoconductive surface. The selectively-charged surface of the photoconductor belt then passes a plurality of individual reservoirs, each supplying a different color of individually-charged toner particles. Multiple colors of charged toner particles from the plurality of individual reservoirs are deposited onto the charged surface of the photoconductor belt. Each color of toner supplied from the individual reservoirs has a charge, and will thus adhere to a particular area on the charged surface of the photoconductor belt in a manner to correspondingly color the electrostatic latent image to form a multi-color toner image.
The multi-color toner image is then transferred directly to an image receiving medium substrate at an image transfer nip formed between the photoconductor belt and a transfer roller. Alternatively, the multi-color toner image may be transferred directly from the photoconductor belt to an intermediate transfer element at an intermediate transfer nip formed between the photoconductor belt and the intermediate transfer element. When transferred from the photoconductor belt to the intermediate transfer element, the toner image may then be transferred from the intermediate transfer element to the image receiving medium substrate at an image transfer nip formed between the intermediate transfer element and a transfer roller.
The image transfer process is completed then by passing the image receiving medium substrate, with the toner image formed thereon, to a fuser unit. The fuser unit is used to fuse and fix the toner image on the image receiving medium substrate through an application of heat and/or pressure in the fuser unit to the transferred toner image on image receiving medium substrate. The image receiving medium substrate, with the toner image fused and fixed thereon, is then passed to an image receiving medium substrate output collection area or tray where the user collects the finished, permanently imaged documents in the image forming device.
Fusing units and modules have become increasingly sophisticated. FIG. 1 illustrates a schematic diagram of an exemplary embodiment of a conventional belt roll fuser 100. Generally, a belt roll fuser may circulate a fuser belt 110 around a series of heated rollers 115,125,135,145, including an internal pressure (or fuser) roller 145. A fusing nip may be formed by contact of the fuser belt 110 as it is sandwiched between the internal pressure (or fuser) roller 145 and an external pressure (or pressure) roller 150. Components of the belt roll fuser 100 typically include a tension roller 115 that cooperates with a belt tensioning unit 120 to provide belt tracking and steering, and belt tension control. A cleaner roller 135 can be provided to cooperate with some form of cleaner unit 130, such as a customer replaceable web belt cleaner, that is usable to remove residual toner and other debris from the fuser belt 110. A metering unit 140 can be provided to condition the fuser belt 110 with oil in operation. A number of thermistors (not shown) can be provided to monitor belt temperature with an objective of promoting even heating of the fuser belt 110.
In operation, the belt roll fuser 100 may receive an image receiving medium substrate from the marking unit (not shown) via an intermediate transport path 155. The intermediate transport path 155 may be aided and supported by some manner of intermediate transport unit 160 to the fusing nip. As the image receiving medium substrate emerges from the fusing nip, it may be aided in separation from the fuser belt 110 by interaction of the fuser belt with a stripping shoe 165, the operation of which may be supplemented by operation of an air knife 170. Because the image receiving medium tends to stick to the fusing belt 110 after passing through the fusing nip, the stripping shoe 165 provides a small, e.g., less than 5 mm, stripping radius such that the image receiving medium substrate is peeled away from the fuser belt 110. The fuser belt 110 wraps around the outside of the stripping shoe 165, and due to size and space constraints, creates three pressure zones as will be described in more detail below. Some form of exit sensor 175 may be provided to sense passage of the image receiving medium substrate to an output transport path 180 over which the image receiving medium substrate may be transported from the fusing unit to an output image receiving medium receptacle by operation of some form of output transport unit 185.